1. Technical Field
The present invention relates to resin-encapsulated type semiconductor packages and production method and apparatus therefor. For example, the invention is favorably used as a method for producing resin-encapsulated type semiconductor packages by encapsulating transistors, semiconductor chips such as IC and LSI, electronic parts, etc. with resin compositions.
2. Prior Art
Heretofore, a transfer molding has been widely used as a known method suitable for encapsulating transistors, semiconductor chips such as IC and LSI, other electronic parts, etc. with epoxy resin encapsulating materials suitably from the standpoint of low costs as well as high reliability and productivity. This is shown in FIG. 15.
According to this transfer molding, the following is a common method. That is, the epoxy resin encapsulating material is preliminarily formed as a tablet, and the tablet 72 is placed in a pot 62 of a molding die 61, and pressed with a feeding plunger while being melted under heating. Thereby, the melt is fed into a molding cavity 63 via various flow paths including a transfer pot, a runner 64 and a gate 65. The epoxy resin encapsulating material is formed and cured and simultaneously a semiconductor package is molded by encapsulating a lead frame 63a to which semiconductor chips or electronic parts are attached.
However, this method is based on the assumption that the epoxy resin encapsulating material is preliminarily formed in the form of the tablet, and therefore additional forming step is necessary. Since such tablets differ depending upon shapes and sizes of products to be formed by molding. Thus, many tablet machines and molding dies are required for such tables. Further, there are problems that tablets are broken during transferring and fine powder attached to surfaces of the tablets scatter on surfaces of molding dies and deteriorate quality of the products.
Furthermore, according to the transfer molding method, most of the resin remaining in the transfer pot, the runner and the gate is disposed of as an unnecessary cured resin, so that there is a limit in increasing a resin efficiency as a ratio of the used encapsulating resin to the total one. Moreover, since tablets need to be stored in different sizes depending upon those of products, it is troublesome to effect inventory control for the tablets. Thus, there is a problem from the standpoint of effective utilization of resources as well as cost performance.
To the contrary, a compression molding method is proposed in which a resin-encapsulating molding die composed of upper and lower split molding dies is maintained at a given high temperature, a thermosetting resin is applied inside the molding die and melted there, a lead frame or a TAB tape having semiconductor chips mounted thereon is fixed in the molding die, and a package is formed by applying pressure upon the molding die. See Patent Document 1, for example.
Another compression molding method is proposed in which an encapsulating resin sheet composed of a non-cured resin is arranged at least on an activating face of semiconductor chips connected to an outside lead-constructing body via bonding wires, and a package is formed by pressing the encapsulating resin sheet upon the semiconductor chips. See Patent Document 2, for example.
Further, a further compression molding method is proposed in which a lead frame or a tape frame having semiconductor chips mounted thereon is inserted into a molding die, a sheet-shaped resin is fed directly into a cavity, and a package is formed under pressure in the state that bottom faces of upper and lower cavities are acting as forming plungers. See Patent Document 3, for example.
A still further compression molding method is proposed in which semiconductor chips provided on a carrier are placed together with a thin plate-shaped resin chip in a molding die composed of upper and lower molding units one of which is opened and closed relative to the other, and a package is formed by pressing the resin chip upon the semiconductor chips. See Patent Document 4, for example.
These four Patent Documents 1 to 4 propose that the compression molding methods can be utilized as semiconductor-sealed body-producing method to cope with requirements that the encapsulating step can be automated in an inline system and suited for enlarged scales, reduced thicknesses, and high integration of packages with high reliability.
However, since the applied resin, the resin sheet or the resin chip is preliminarily heated on the molding die at a high temperature of around 170° C. for a given time period and then subjected to compression molding, there exists a problem that metal wires are deformed due to increase in viscosity with progress in curing of the encapsulating resin. Further, as to the transfer molding, there are problems that apparatuses for producing the tablets, the resin sheets or the resin chips are needed and resulting tablets, resin sheets or resin chips are required to be stored.
Patent Document 1: JP-A 8-111465 (page 2 to 5)
Patent Document 2: JP-A 6-275767 (pages 2 to 9)
Patent Document 3: JP-A 8-330342 (Pages 2 to 6)
Patent Document 4: JP-A 9-187831 (pages 2 to 10)